Nitride light emitting device and manufacturing method thereof

ABSTRACT

A nitride LED having a laminated structure in which a substrate, a n-type cladding layer, an active layer, a p-type cladding layer, and a multi-ohmic contact layer are sequentially stacked, and a manufacturing method thereof, are provided. In the nitride LED, the multi-ohmic contact layer includes multiple layers of a first transparent film layer/silver/second transparent film layer. In the nitride LED and a manufacturing method thereof, ohmic contact characteristics with respect to the p-type cladding layer are enhanced, thereby exhibiting a good current-voltage characteristic. Also, since the transparent electrodes have a high light transmitting property, the light emitting efficiency of the device is increased.

BACKGROUND OF THE INVENTION

This application claims the priority of Korean Patent Application No.2003-95957, filed on Dec. 24, 2003, in the Korean Intellectual PropertyOffice, the disclosure of which is incorporated herein in its entiretyby reference.

1. Field of the Invention

The present invention relates to a nitride light emitting device (LED)and a manufacturing method thereof, and more particularly, to a nitrideLED having an electrode structure of improved emission efficiency andenhanced driving capability and a manufacturing method thereof.

2. Description of the Related Art

Currently, transparent conductive films are used in variousapplications, including photoelectronic devices, displays, or energyindustry.

In the field of LEDs, there has been developed a transparent conductivefilm electrode for smooth hole injection and high-efficiency lightemission.

Currently, transparent conducting oxide (TCO), transparent conductingnitride (TCN), and the like, are most actively researched as transparentconductive film materials.

Examples of the transparent conductive oxide include indium oxide(In₂O₃), tin oxide (SnO₂), zinc oxide (ZnO), indium tin oxide (ITO), andthe like, and examples of the transparent conductive nitride includetitanium nitride (TiN), and the like.

These materials, however, have limitations to be employed alone as ap-type transparent electrode of a top-emitting gallium nitride based LEDbecause they have a relatively large sheet resistance value, high lightreflectivity, and a relatively small work function value.

That is to say, the above-noted transparent conductive films, which havea relatively large sheet resistance, that is, substantially 100 Ω/° C.,may make it difficult for a LED to perform current spreading in ahorizontal direction with respect to the LED, that is, in a directionparallel to an interface surface of the LED, during film formation usingPVD such as sputtering, e-beam evaporation, or a heat evaporation. Inaddition, the transparent conductive film makes it difficult to achievevertical injection of holes smoothly in a vertical direction. Thus, suchtransparent conductive films are limited in achieving large-area,large-capacity, high brightness LEDs.

Further, the above-mentioned transparent conductive films deterioratelight emitting efficiency because they have high reflectivity withrespect to light emitted from the gallium nitride based LEDs.

Next, since transparent conductive films, including indium tin oxide(ITO), titanium nitride (TiN), and the like, have a relatively smallwork function value, it is quite difficult to form an ohmic contactthrough a direct contact with p-type gallium nitride.

Finally, when transparent conductive oxide (TCO) is employed as anelectrode such that it is brought into a direct ohmic contact with agallium nitride based compound semiconductor, oxidation of gallium islikely to occur on a gallium nitride surface during formation of a film,resulting in generation of gallium oxide (Ga₂O₃), which is an insulatingmaterial, making it difficult to form a good ohmic-contact electrode.

Meanwhile, in achieving a LED prepared from a gallium nitride basedcompound semiconductor or a laser diode (LD), the structure of anelectrode for forming an ohmic contact between the semiconductor and theelectrode becomes quite an important factor.

Such gallium nitride based LEDs are classified as top-emitting lightemitting diodes (TLEDS) and flip-chip light emitting diodes (FCLEDS).

In the TLEDS, which are currently widely used, light is emitted throughan ohmic contact layer being in contact with a p-type cladding layer. Inorder to achieve high-brightness TLEDS, one requirement is to form acurrent spreading film, that is, a current spreading layer, as a goodohmic contact layer for compensating for a high level of sheetresistance of the p-type cladding layer having a low hole concentration.Therefore, it is necessary to provide for smooth hole injection, currentspreading, and high light emission performance by forming a currentspreading film layer having a low sheet resistance value and a highdegree of light transmittance.

The known TLEDS have an electrode structure in which a nickel (Ni) layerand a gold (Au) layer are sequentially laminated on a p-type claddinglayer.

The nickel/gold layer structure has good specific contact resistance ina range of about 10⁻³ to about 10⁻⁴ Ω° C., and is used as asemi-transparent ohmic contact layer.

When such a nickel/gold layer structure is annealed at a temperature ofabout 500° C. to about 600° C. under an oxygen atmosphere, nickel oxide(NiO), i.e., p-type semiconductor oxide, is formed at an interfacebetween a gallium nitride based p-type cladding layer and a nickel layeras an ohmic contact in an island shape, thereby reducing a Schottkybarrier height (SBH) and easily supplying holes as multiple carriers toa region around the p-type cladding layer.

In addition, annealing of the nickel/gold layer, followed by forming thep-type cladding layer, removes a Mg—H intermetallic compound forreactivation of increasing a magnesium dopant concentration on a galliumnitride surface, thereby increasing the concentration of effectivecarriers on the surface of the p-type cladding layer to 10¹⁸ or greater.The increased concentration of effective carriers is believed to causetunneling conductance between the p-type cladding layer and the ohmiccontact layer containing nickel oxide, exhibiting an ohmic conductingcharacteristic with low specific contact resistance.

However, the TLEDS using a semi-transparent nickel/gold film electrodeis poor in light emitting efficiency due to presence of a lighttransmittance suppressing component, that is gold (Au), which is alimitation in achieving next-generation large capacity, high-brightnessLEDs.

To increase emission of heat generated during operation of a LED andlight emission efficiency, a reflective layer has been employed toradiate light through a transparent substrate made of sapphire in theFCLEDS structure, which, however, has several limitations, includinghigh resistance due to oxidation and poor adhesion of the reflectivelayer.

To overcome such problems with the TLEDS or FCLEDS structure,transparent conductive oxide having better transmittance than asemi-transparent nickel/gold layer structure used for the existingp-type ohmic contact layer, e.g., ITO, has been proposed as a materialfor a p-type ohmic contact layer. However, although the ITO ohmiccontact layer increases the output power of the LED, it requires arelatively high operation voltage, which is still a limitation as acandidate material for use in large-area, high-capacity, high-brightnessLEDs.

As described above, it is quite difficult to develop a transparentelectrode for establishing an ohmic contact for several reasons thatfollow.

First, low hole concentration and high sheet resistance of not less than10⁴ Ω/° C. of p-type gallium nitride make it difficult to form atransparent electrode.

Second, since there is no transparent electrode material having arelatively high work function value than that of p-type gallium nitride,a high schottky barrier is formed at an interface between p-type galliumnitride and the electrode, thereby making smooth hole injectiondifficult.

Third, most of transparent electrode materials exhibit contradictoryelectrical and optical characteristics and have a high degree of lighttransmittance, so that they typically have large sheet resistance,thereby sharply reducing a tendency of horizontal current spreading.Accordingly, a large amount of heat is generated between p-type galliumnitride and the transparent electrode, shortening the life of a deviceand impairing the reliability in the operation of the device.

SUMMARY OF THE INVENTION

The present invention provides a nitride LED having an electrodestructure which exhibits a high light-transmitting property and having alow sheet resistance.

According to an aspect of the present invention, there is provided anitride light emitting device (LED) having an active layer between an-type cladding layer and a p-type cladding layer, comprising amulti-ohmic contact layer on the p-type cladding layer, wherein themulti-ohmic contact layer comprises a first transparent film layerformed on the p-type cladding layer, a metallic layer containing silveras a main component on the first transparent film layer, and a secondtransparent film layer formed on the metallic layer, and wherein thefirst transparent film layer and the second transparent film layer areformed of one selected from the group consisting of a transparent oxide,a transparent nitride, and a transparent dielectric.

The transparent oxide may be an oxide containing at least one selectedfrom the group consisting of a binary oxide or a ternary oxide formed ofoxygen and at least one element selected from the group consisting ofindium (In), tin (Sn), gallium (Ga), cadmium (Cd), aluminum (Al) andvanadium (V).

The ternary oxide may be at least one selected from the group consistingof indium-nickel oxide (In—Ni—O), indium-copper oxide (In—Cu—O),indium-rhodium oxide (In—Rh—O), indium-iridium oxide (In—Ir—O),indium-ruthenium oxide (In—Ru—O), tin-nickel oxide (Sn—Ni—O), tin-copperoxide (Sn—Cu—O), tin-rhodium oxide (Sn—Rh—O), tin-iridium oxide(Sn—Ir—O), tin-ruthenium oxide (Sn—Ru—O), zinc-nickel oxide (Zn—Ni—O),zinc-copper oxide (Zn—Cu—O), zinc-rhodium oxide (Zn—Rh—O), zinc-iridiumoxide (Zn—Ir—O), zinc-ruthenium oxide (Zn—Ru—O), zinc-tin oxide(Zn—Sn—O), zinc-aluminum oxide (Zn—Al—O), magnesium-indium oxide(Mg—In—O), magnesium-tin oxide (Mg—Sn—O), magnesium-zinc oxide(Mg—Zn—O), gallium-indium oxide (Ga—In—O), lanthanum-copper oxide(La—Cu—O), strontium-copper oxide (Sr—Cu—O), copper-aluminum oxide(Cu—Al—O), copper-gallium oxide (Cu—Ga—O), silver-indium oxide(Ag—In—O), silver-tin oxide (Ag—Sn—O), silver-zinc oxide (Ag—Zn—O),indium-cesium oxide (In—Ce—O), tin-antimony oxide (Sn—Sb—O), andvanadium-zinc oxide (V—Zn—O).

The transparent nitride may be formed of a nitrogen (N), and at leastone selected from the group consisting of titanium (Ti), vanadium (V),chromium (Cr), zirconium (Zr), hafnium (Hf), tantalum (Ta), tungsten(W), molybdenum (Mo), and scandium (Sc),

The transparent dielectric may be one selected from the group consistingof ZnS, ZnTe, ZnSe, and MgF₂, which is good in anti-reflectivity.

Each of the respective transparent film layers preferably has athickness of 1 to 1000 nm.

In order to adjust electrical properties of the transparent film layer,the transparent film layer may further include a dopant. Here, thedopant is preferably an element classified as a metal in the periodictable of the elements.

The amount of the dopant added to the transparent conductive oxide ispreferably in a range from 0.001 to 20 wt %.

The metal layer is preferably formed to a thickness of 1 to 20 nm.

More preferably, the nitride LED further comprises an intermediate layerbetween the p-type cladding layer and the first transparent film layer,the intermediate layer being formed of at least one element selectedfrom the group consisting of nickel (Ni), cobalt (Co), Zinc (Zn),palladium (Pd), platinum (Pt), copper (Cu), iridium (Ir), and ruthenium(Ru), an alloy containing the selected element, an oxide, and a solidsolution.

In forming the intermediate layer, the transparent oxide may be employedas the first and second transparent film layers, and preferred examplesthereof include binary oxides, ternary oxides, and the like, the binaryoxides consisting of oxygen and at least one element selected from thegroup consisting of indium (In), tin (Sn), gallium (Ga), cadmium (Cd),aluminum (Al), zinc (Zn), magnesium (Mg), beryllium (Be), silver (Ag),molybdenum (Mo), vanadium (V), copper (Cu), iridium (Ir), rhodium,ruthenium (Ru), tungsten (W), cobalt (Co), nickel (Ni), manganese (Mn),and lanthanum (La).

The intermediate layer is preferably formed to a thickness of 0.1 to 20nm.

In another embodiment of the present invention, the nitride LED mayfurther comprise a reflective layer on the multi-ohmic contact layer,the reflective layer being formed of at least one element selected fromthe group consisting of silver (Ag), silver oxide (AgO₂), aluminum (Al),zinc (Zn), magnesium (Mg), ruthenium (Ru), titanium (Ti), ruthenium(Rh), chromium (Cr), and platinum (Pt).

The reflective layer is preferably formed to a thickness of 100 to 1000nm.

In order to prevent a multi ohmic contact layer from being damagedduring annealing and packaging processes, the nitride LED may furthercomprise an agglomeration preventing layer on the reflective layer, theagglomeration preventing layer being formed of at least one elementselected from the group consisting of nickel (Ni), zinc (Zn), magnesium(Mg), platinum (Pt), copper (Cu), palladium (Pd), chromium (Cr), andtungsten (W), an alloy containing the selected element, an oxide, asolid solution, and titanium nitride (TiN).

The agglomeration preventing layer is preferably formed to a thicknessof 10 to 1000 nm.

In accordance with another aspect of the present invention, there isprovided a method of manufacturing a nitride light emitting device (LED)having an active layer between a n-type cladding layer and a p-typecladding layer, the method comprising: (a) forming a multi-ohmic contactlayer on a substrate by sequentially depositing a first transparent filmlayer, a metallic layer containing silver as a main component, and asecond transparent film layer on the p-type cladding layer; and (b)annealing the resultant product of step (a), wherein the firsttransparent film layer and the second transparent film layer are formedof one selected from the group consisting of a transparent oxide, atransparent nitride, and a transparent dielectric.

In another embodiment of the present invention, the method may furthercomprising forming a reflective layer on the multi ohmic contact layerfor realization of FCLEDS.

In addition, in order to prevent a multi ohmic contact layer from beingdamaged during annealing and packaging processes, the method may furthercomprise forming an agglomeration preventing layer on the reflectivelayer.

The annealing is preferably performed at a temperature of 20° C. to1500° C.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present inventionwill become more apparent by describing in detail exemplary embodimentsthereof with reference to the attached drawings in which:

FIG. 1 is a cross-sectional view of a LED having a p-type electrodestructure according to a first embodiment of the present invention;

FIG. 2 is a graphical representation showing current-voltagecharacteristics of the p-type electrode structure according to a firstembodiment of the present invention;

FIG. 3 is a cross-sectional view of a LED having a p-type electrodestructure according to a second embodiment of the present invention;

FIG. 4 is a cross-sectional view of a LED having a p-type electrodestructure according to a third embodiment of the present invention;

FIG. 5 is a cross-sectional view of a LED having a p-type electrodestructure according to a fourth embodiment of the present invention; and

FIG. 6 is a cross-sectional view of a LED having a p-type electrodestructure according to a sixth embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, a nitride LED according to an exemplary embodiment of thepresent invention and a manufacturing method thereof will be describedin more detail with reference to the accompanying drawings.

Like numbers refer to like elements throughout the drawings referred toin the description of the invention.

FIG. 1 is a cross-sectional view of a LED having a p-type electrodestructure according to a first embodiment of the present invention.

Referring to FIG. 1, the LED is constructed such that a substrate 110, abuffer layer 120, a n-type cladding layer 130, an active layer 140, ap-type cladding layer 150, and a multi-ohmic contact layer 230 aresequentially laminated.

Reference numeral 180 denotes a p-type electrode pad, and referencenumeral 190 denotes a n-type electrode pad.

A light emitting structure consists of layers ranging from the substrate110 to the p-type cladding layer 150, and a p-type electrode structureconsists of layers laminated on the p-type cladding layer 150.

The substrate 110 is preferably formed of any one selected from thegroup consisting of sapphire (Al₂O₃), silicon carbide (SiC), silicon(Si), and gallium arsenide (GaAs).

The buffer layer 120 may not be provided on the laminated structure.

The respective layers ranging from the buffer layer 120 to the p-typecladding layer 150 are based on any one selected from compoundsrepresented by Al_(x)In_(y)Ga_(z)N, where 0≦x≦1, 0≦y≦1, 0≦z≦1, and0≦x+y+z≦1, corresponding to the general formula of Group ° C. nitridecompounds, and the n-type cladding layer 130 and the p-type claddinglayer 150 further include corresponding dopants.

The active layer 140 may be formed of a single layer or a multiplequantum well (MQW) by various known methods.

For example, when the buffer layer 120 is formed of GaN, the n-typecladding layer 130 comprises GaN, and Si, Ge, Se, or Te, added as an-type dopant, the active layer 140 comprises InGaN/GaN MQW or AlGaN/GaNMQW, and the p-type cladding layer 150 comprises GaN, and Mg, Zn, Ca,Sr, or Ba as a p-type dopant.

A n-type ohmic contact layer (not shown) may be interposed between then-type cladding layer 130 and the n-type electrode pad 190, and then-type ohmic contact layer may have a variety of structures, forexample, a laminated structure in which titanium (Ti) and aluminum (Al)are sequentially laminated.

The p-type electrode pad 180 may have a laminated structure of nickel(Ni)/gold (Au), or silver (Ag)/gold (Au).

The respective layers may be formed by e-beam evaporation, physicalvapor deposition (PVD), chemical vapor deposition (CVD), plasma laserdeposition (PLD), dual-type thermal evaporation, sputtering, and so on.

The multi-ohmic contact layer 230 has a p-type electrode structure inwhich a first transparent film layer 230 a, a metallic layer 230 b, anda second transparent film layer 230 c are sequentially laminated.

The first transparent film layer 230 a and the second transparent filmlayer 230 c are formed of transparent oxide, transparent nitride, or atransparent dielectric.

According to a feature of the present invention, the transparent oxideis a binary oxide, or a ternary oxide, in which any one selected fromthe group consisting of indium (In), tin (Sn), gallium (Ga), cadmium(Cd), aluminum (Al), and vanadium (V), is combined with oxygen (O).

The ternary oxide may be at least one selected from the group consistingof indium-nickel oxide (In—Ni—O), indium-copper oxide (In—Cu—O),indium-rhodium oxide (In—Rh—O), indium-iridium oxide (In—Ir—O),indium-ruthenium oxide (In—Ru—O), tin-nickel oxide (Sn—Ni—O), tin-copperoxide (Sn—Cu—O), tin-rhodium oxide (Sn—Rh—O), tin-iridium oxide(Sn—Ir—O), tin-ruthenium oxide (Sn—Ru—O), zinc-nickel oxide (Zn—Ni—O),zinc-copper oxide (Zn—Cu—O), zinc-rhodium oxide (Zn—Rh—O), zinc-iridiumoxide (Zn—Ir—O), zinc-ruthenium oxide (Zn—Ru—O), zinc-tin oxide(Zn—Sn—O), zinc-aluminum oxide (Zn—Al—O), magnesium-indium oxide(Mg—In—O), magnesium-tin oxide (Mg—Sn—O), magnesium-zinc oxide(Mg—Zn—O), gallium-indium oxide (Ga—In—O), lanthanum-copper oxide(La—Cu—O), strontium-copper oxide (Sr—Cu—O), copper-aluminum oxide(Cu—Al—O), copper-gallium oxide (Cu—Ga—O), silver-indium oxide(Ag—In—O), silver-tin oxide (Ag—Sn—O), silver-zinc oxide (Ag—Zn—O),indium-cesium oxide (In—Ce—O), tin-antimony oxide (Sn—Sb—O), andvanadium-zinc oxide (V—Zn—O). Here, the respective components arecombined with each other in the oxide in an appropriate ratio.

The transparent nitride is in a combination of at least one metalselected from the group consisting of titanium (Ti), vanadium (V),chromium (Cr), zirconium (Zr), hafnium (Hf), tantalum (Ta), tungsten(W), molybdenum (Mo), and scandium (Sc), and nitrogen (N). Thetransparent dielectric is any one selected from the group consisting ofZnS, ZnTe, ZnSe, and MgF₂.

Materials used for the transparent film layers 230 a and 230 c areselected in consideration of work function and sheet resistance.

In order to improve electrical properties of transparent oxide,transparent nitride, and transparent dielectric used as main componentsof the transparent film layers 230 a and 230 c, at least one elementamong metal constituents shown in the periodic table of the elements maybe added as a dopant.

Here, the ratio of the dopant added to impart appropriate electricproperties to the transparent oxide, transparent nitride, transparentdielectric is preferably in a range of 0.001 to 20 wt %. Here, “wt %”stands for percentage by weight among elements added.

The first and second transparent film layers 230 a and 230 c arepreferably formed to a thickness in a range of 1 nm to 1000 nm from theviewpoint of appropriate degrees of light transmittance and electricconductivity.

The metallic layer 230 b is made from a material which has high electricconductivity, is easily decomposed to conductive, nano-phase particlesduring annealing at a temperature of not greater than 600° C. under anoxygen atmosphere, and is not liable to oxidation.

One exemplary material for the metallic layer 230 b satisfying suchconditions is silver (Ag).

The metallic layer 230 b is preferably formed of a single substance. Themetallic layer 230 b may also be formed of an alloy or solid solutionhaving silver (Ag) as a main component.

The metallic layer 230 b of the multi-ohmic contact layer 230 ispreferably formed to a thickness enough to be easily decomposed toconductive, nano-phase particles during annealing, that is, a thicknessin a range of 1 nm to 20 nm.

The multi-ohmic contact layer 230 is preferably formed by any techniqueamong e-beam evaporation, thermal evaporation, sputtering deposition,pulsed laser deposition, and the like.

In addition, the deposition temperature for forming the multi-ohmiccontact layer 230 is preferably in a range of approximately 20° C. toapproximately 1500° C., and the pressure of an evaporator is preferablyin a range of atmospheric pressure to approximately 10⁻¹² Torr.

The forming of the multi-ohmic contact layer 230 is preferably followedby annealing.

The annealing is preferably carried out at a temperature ofapproximately 100° C. to approximately 800° C. under vacuum or gaseousatmosphere for approximately 10 seconds to approximately 3 hours.

During annealing, at least one gas selected among nitrogen, argon,helium, oxygen, hydrogen, air, and so on may be injected into thereaction chamber.

FIG. 2 is a graphical representation showing current-voltagecharacteristics of the p-type electrode structure according to a firstembodiment of the present invention, in which a LED is constructed suchthat a first transparent film layer 230 a made of indium tin oxide (ITO)is deposited on a p-type cladding layer 150, a metallic layer made ofsilver is deposited thereon, and a second transparent film layer 230 cmade of indium tin oxide (ITO) are deposited thereon, and a LED isconstructed such that indium tin oxide (ITO) is formed alone on thep-type cladding layer 150 to form an ohmic contact layer.

As shown in FIG. 2, the current-voltage characteristic of the LED havingthe multi-ohmic contact layer 230 according to the present invention isbetter than that of the LED having indium tin oxide (ITO) alone.

When indium tin oxide (ITO) is used alone as an electrode material, thesheet resistance of the electrode is 87 Ω/□. When the multi-ohmiccontact layer 230 has an electrode structure of ITO/Ag/ITO, the sheetresistance thereof structure is reduced to 8 Ω/° C.

This result confirms that as the sheet resistance of a film layer usedas the electrode structure becomes smaller, lateral current spreadingeasily occurs, suggesting that a reliable LED having high light emissionefficiency is achievable.

FIG. 3 is a cross-sectional view of a LED having a p-type electrodestructure according to a second embodiment of the present invention;

Referring to FIG. 3, the LED may further include an intermediate layer220 between the multi-ohmic contact layer 230 and the p-type claddinglayer 150.

Here, the p-type electrode structure includes an intermediate layer 220and a multi-ohmic contact layer 230.

The intermediate layer 220 is formed of a material capable of increasingelectric conductivity and ohmic contact characteristics between themulti-ohmic contact layer 230 and the p-type cladding layer 150 andforming gallium-associated compounds.

Preferably, the intermediate layer is formed of any one material amongat least one element selected from the group consisting of nickel (Ni),cobalt (Co), Zinc (Zn), palladium (Pd), platinum (Pt), copper (Cu),iridium (Ir), and ruthenium (Ru), alloys containing the at least oneselected element, oxides, and a solid solution.

Preferably, the intermediate layer 220 is formed to a thickness of 0.1nm to 20 nm.

When the intermediate layer 220 is formed, usable examples of thetransparent oxide used as the transparent film layers 230 a and 230 cinclude binary or ternary oxides formed of oxygen and at least oneelement selected from the group consisting of indium (In), tin (Sn),Zinc (Zn), gallium (Ga), cadmium (Cd), magnesium (Mg), beryllium (Be),silver (Ag), molybdenum (Mo), vanadium (V), copper (Cu), iridium (Ir),rhodium, ruthenium (Ru), tungsten (W), cobalt (Co), nickel (Ni),manganese (Mn), aluminum (Al), and lanthanum (La). As the ternary oxide,the oxide described with reference to FIG. 1 may be used.

FIG. 4 is a cross-sectional view of a LED having a p-type electrodestructure according to a third embodiment of the present invention.

Referring to FIG. 4, the LED has a reflective layer 240 formed on amulti-ohmic contact layer 230.

Here, the p-type electrode structure includes the multi-ohmic contactlayer 230 and the reflective layer 240.

The reflective layer 240 is used to realize FCLEDS, and preferablyformed of at least one selected from the group consisting of silver(Ag), silver oxide (Ag₂O), aluminum (Al), Zinc (Zn), magnesium (Mg),ruthenium (Ru), titanium (Ti), ruthenium (Rh), chromium (Cr), andplatinum (Pt).

The reflective layer 240 is formed to a thickness of 100 nm to 1000 nmin view of reflectivity.

In addition, the reflective layer 240 may be employed additionally tothe LED shown in FIG. 3. That is, in the LED shown in FIG. 3, thereflective layer 240 may further be formed on the multi-ohmic contactlayer 230 disposed on the intermediate layer 220 using the same materialas described above.

FIG. 5 is a cross-sectional view of a LED having a p-type electrodestructure according to a fourth embodiment of the present invention.

Referring to FIG. 5, the LED has an electrode structure in which areflective layer 240 and an agglomeration preventing layer 250 aresequentially laminated on the multi-ohmic contact layer.

The agglomeration preventing layer 250 is employed to increaseadhesiveness between the same and a p-type electrode pad 180 and toenhance durability by suppressing oxidation of the reflective layer 240.

The agglomeration preventing layer 250 is preferably formed of at leastone selected from the group consisting of an element selected amongnickel (Ni), Zinc (Zn), magnesium (Mg), platinum (Pt), copper (Cu), andpalladium (Pd), an alloy containing the selected element, oxide, a solidsolution, and titanium nitride (TiN).

The agglomeration preventing layer 250 is preferably formed to athickness of 100 nm to 1000 nm.

FIG. 6 is a cross-sectional view of a LED having a p-type electrodestructure according to a fifth embodiment of the present invention.

Referring to FIG. 6, the Led has an electrode structure in which anintermediate layer 220, a multi-ohmic contact layer 230, a reflectivelayer 240, and an agglomeration preventing layer 250 are sequentiallylaminated on a p-type cladding layer 150.

The LED illustrated in FIGS. 3 through 6 is formed by depositing eachcorresponding p-type electrode structure on the LED structure ofmultiple layers ranging from the substrate 110 to the p-type claddinglayer 150 by the deposition technique described with reference to FIG.1, followed by annealing.

Performing the annealing improves the current-voltage characteristic ofthe device compared to the case in which the annealing is not performed.

As described above, in the nitride LED and the manufacturing methodthereof, the multi-ohmic contact layer includes multiple layers of afirst transparent film layer/silver/second transparent film layer. Inaddition, ohmic contact characteristics with respect to the p-typecladding layer are enhanced, thereby exhibiting a good current-voltagecharacteristic. Also, since the transparent electrodes have a high lighttransmitting property, the light emitting efficiency of the device isincreased.

While the present invention has been particularly shown and describedwith reference to exemplary embodiments thereof, it will be understoodby those of ordinary skill in the art that various changes in form anddetails may be made therein without departing from the spirit and scopeof the present invention as defined by the following claims.

1-8. (canceled)
 9. A method of manufacturing a nitride light emittingdevice (LED) having an active layer between a n-type cladding layer anda p-type cladding layer, the method comprising: (a) forming amulti-ohmic contact layer on a substrate by sequentially depositing afirst transparent film layer, a metallic layer containing silver as amain component, and a second transparent film layer on the p-typecladding layer; and (b) annealing the resultant product of step (a),wherein the first transparent film layer and the second transparent filmlayer are formed of one selected from the group consisting of atransparent oxide, a transparent nitride, and a transparent dielectric.10. The method of claim 9, wherein the transparent oxide is an oxidecontaining at least one selected from the group consisting of indium(In), tin (Sn), gallium (Ga), cadmium (Cd), vanadium (V), and aluminum(Al), the transparent nitride is formed of a nitrogen (N), and at leastone selected from the group consisting of titanium (Ti), vanadium (V),chromium (Cr), zirconium (Zr), hafnium (Hf), tantalum (Ta), tungsten(W), molybdenum (Mo), and scandium (Sc), and the transparent dielectricis one selected from the group consisting of ZnS, ZnTe, ZnSe, and MgF₂.11. The method of claim 9, before forming the first transparent filmlayer, further comprising forming an intermediate layer on the p-typecladding layer, the intermediate layer being formed of at least oneelement selected from the group consisting of nickel (Ni), cobalt (Co),Zinc (Zn), palladium (Pd), platinum (Pt), copper (Cu), iridium (Ir), andruthenium (Ru), an alloy containing the selected element, an oxide, anda solid solution.
 12. The method of claim 11, wherein the oxide isformed of at least one element selected from the group consisting ofindium (In), tin (Sn), gallium (Ga), cadmium (Cd), aluminum (Al), zinc(Zn), magnesium (Mg), beryllium (Be), silver (Ag), molybdenum (Mo),vanadium (V), copper (Cu), iridium (Ir), rhodium, ruthenium (Ru),tungsten (W), cobalt (Co), nickel (Ni), manganese (Mn), and lanthanum(La).
 13. The method of claim 9, further comprising forming a reflectivelayer on the multi-ohmic contact layer, the reflective layer beingformed of at least one element selected from the group consisting ofsilver (Ag), silver oxide (AgO₂), aluminum (Al), zinc (Zn), magnesium(Mg), ruthenium (Ru), titanium (Ti), ruthenium (Rh), chromium (Cr), andplatinum (Pt).
 14. The method of claim 13, further comprising forming anagglomeration preventing layer on the reflective layer, theagglomeration preventing layer being formed of at least one elementselected from the group consisting of nickel (Ni), zinc (Zn), magnesium(Mg), platinum (Pt), copper (Cu), palladium (Pd), chromium (Cr), andtungsten (W), an alloy containing the selected element, an oxide, asolid solution, and titanium nitride (TiN).